JP2878497B2 - Manufacturing method of adhesive for electroless plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electroless plating adhesive used for producing a printed wiring board.

[0002]

2. Description of the Related Art In recent years, miniaturization, high performance, and multifunctionality of electronic devices have been promoted, and high density and high reliability by fine patterns have been demanded for printed wiring boards used therein. I have.

Conventionally, as a method of forming a conductive circuit on a printed wiring board, a subtractive method of forming a conductive circuit by laminating a copper foil on an insulating substrate and then performing photoetching has been widely used. According to this method, a conductor circuit having excellent adhesion to an insulating substrate can be formed. However, a so-called undercut occurs due to etching due to the thickness of the copper foil, and it is difficult to obtain a high-precision fine pattern. There is a problem that it is difficult to cope with this.

[0004] For this reason, as an alternative to the subtractive method, an adhesive is applied to an insulating substrate to form an adhesive layer, the surface of the adhesive layer is roughened, and electroless copper plating is applied to form a conductor circuit. The additive method to form is drawing attention.
JP-A-61-276875 discloses a matrix resin solution (heat-resistant resin solution) which becomes hardly soluble in a dissolving solution (oxidizing agent) by a curing treatment as an adhesive for electroless plating used in the additive method. Among them, there has been proposed an adhesive in which two types of fillers having different average particle diameters, which are soluble in the solution and hardly soluble in the matrix resin solution, are dispersed. Conventionally, a matrix resin liquid as a raw material and two types of fillers having different average particle sizes have been mixed at once by three rollers to produce an adhesive.

[0005] In this adhesive, two kinds of fillers are uniformly dispersed in the matrix resin, so that the adhesive strength between the adhesive layer formed by the adhesive and the electroless plating layer formed thereon is enhanced. It is an indispensable condition. This is because the surface was roughened by applying an adhesive to the surface of the substrate, drying and curing to form an adhesive layer, immersing the surface of the adhesive layer in an oxidizing agent and dissolving and removing a part of the surface. An adhesive layer is obtained, and an electroless plating layer is formed on the adhesive layer. Then, the adhesive layer 2 formed on the surface of the substrate 1 is provided in a matrix 3 made of a heat-resistant resin that is hardly soluble in the oxidizing agent.
When b is a uniformly dispersed structure as shown in FIG.
When the surface of the adhesive layer 2 is immersed in an oxidizing agent and a part thereof is dissolved and removed, as shown in FIG. 2, the dissolution of the large filler 4b and the surrounding part 5b formed by dissolving the matrix 3 around the filler 4b Due to the dissolution of the small filler 4a, the concave portion 5 having a complicated shape in which the portion 5a is continuous is formed, and the adhesive strength between the electroless plating layer (not shown) and the adhesive layer 2 is improved. The shape of the recess 5 is controlled by changing the diameter and the mixing ratio of the small filler 4a and the large filler 4b.

[0006]

However, in the mixing method using three rolls, since the crushing force is due to the shearing force, the dispersing force is high, but lot differences easily occur. There is a problem that it costs.

As a method for mixing the filler with the matrix resin liquid, there is a method using a continuous ball mill (sand mill) in addition to the method using three rolls. When a continuous ball mill is used, it is suitable for obtaining a large amount of products of the same quality with a small lot difference. However, since the crushing force is due to the collision force, the dispersing force is not high, and it takes a long kneading time to uniformly disperse the fine particles having an average particle diameter of 1 μm or less, which are easily aggregated, in the matrix resin liquid. Fine particles having an average particle diameter of 2 μm or more are easily pulverized when subjected to a long-time kneading action by a continuous ball mill. Then, fine particles having an average particle size of 1 μm or less and fine particles having an average particle size of 2 μm or more are simultaneously added to the matrix resin liquid, and the average particle size is 1 μm or less.
When kneading with a continuous ball mill until fine particles of μm or less are uniformly dispersed in the matrix resin liquid, the average particle diameter is 2 μm.
m or more are crushed. Therefore, as shown in FIG. 3A, the matrix 3 of the adhesive layer 2 does not include the large filler 4b which is indispensable for forming the concave portion 5 having a complicated shape when the surface of the adhesive layer 2 is roughened. The problem arises.

On the other hand, if the kneading time by a continuous ball mill is shortened in order to prevent the fine particles having an average particle size of 2 μm or more from being pulverized, the fine particles having an average particle size of 1 μm or less become insufficiently crushed, as shown in FIG. As shown in b), in the matrix 3 of the adhesive layer 2, a state in which small fillers 4a essential for forming the concave portions 5 having a complicated shape when the surface of the adhesive layer 2 is roughened is uniformly dispersed. There is a problem that it cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object a matrix comprising a filler having an average particle size of 1 μm or less which is difficult to crush and a filler having an average particle size of 2 μm or more which is easily broken. An object of the present invention is to provide a method for producing an adhesive for electroless plating which can be uniformly mixed with a resin liquid without destruction of a filler.

[0010]

According to the first aspect of the present invention, there is provided a matrix resin liquid which is hardly soluble in a solution by a curing treatment, and a matrix resin which is hardly soluble in the solution. When kneading two kinds of fillers having different average particle diameters which are insoluble and hardly soluble in the matrix resin liquid by a continuous ball mill, the smaller filler having an average particle diameter of 1 μm or less is first mixed with the matrix resin liquid. After that, the larger filler having an average particle diameter of 2 μm or more was added to the mixture, and the mixture was mixed again and dispersed.

Further, in the invention according to the second aspect, a matrix resin solution which is hardly soluble in a solution by a curing treatment, and a matrix resin solution which is soluble in the solution and hardly soluble in the matrix resin solution. When kneading two kinds of fillers having different average particle diameters with a continuous ball mill, the smaller filler having an average particle diameter of 1 μm or less was immersed in a solvent of the matrix resin liquid before kneading with a continuous ball mill. After performing the ultrasonic treatment in the state, the mixing treatment was performed by a continuous ball mill, the larger filler and the matrix resin liquid were added to the treatment liquid, and the mixing treatment was performed again.

According to the third aspect of the present invention, there is provided a matrix resin solution which becomes hardly soluble in a solution by a curing treatment, and a matrix resin solution which is soluble in the solution and hardly soluble in the matrix resin solution. When kneading two kinds of fillers having different average particle diameters in a continuous ball mill, first, a smaller filler having an average particle diameter of 1 μm or less and a solvent of the matrix resin liquid are mixed and dispersed. The matrix resin liquid and the larger filler having an average particle diameter of 2 μm or more were added to the mixture, and the mixture was mixed again and dispersed.

The matrix resin constituting the adhesive is excellent in heat resistance, electrical insulation, chemical stability and adhesiveness, and can be cured by a curing treatment to dissolve a liquid (for example, an oxidizing agent such as a chromic acid aqueous solution). Any resin having the property of being hardly soluble can be used.Especially, it is preferably at least one selected from an epoxy resin, an epoxy-modified polyimide resin, a polyimide resin, and a phenol resin. May be those obtained by imparting photosensitivity (in particular, ultraviolet curability) to these resins.

As the matrix resin liquid, an uncured heat-resistant resin liquid containing no solvent can be used as it is. However, a heat-resistant resin liquid obtained by dissolving a heat-resistant resin in a solvent has a low viscosity, and thus has a low viscosity. Coating work on the surface becomes easier.
As the solvent, methyl ethyl ketone, methyl cellosolve, butyl cellosolve acetate, tetralin, dimethylformamide and the like are used.

The material of the filler mixed with the matrix resin solution is soluble in the solution, hardly soluble or insoluble in the uncured matrix resin solution, and is excellent in heat resistance, electrical insulation, and chemical stability. Need to be. Such materials include cured epoxy resin, polyester resin,
Bismaleimide / triazine resins and the like can be mentioned.

The larger filler is preferably 3 to 20 times the filler having a smaller average particle size, and the average particle size is preferably 10 μm or less.

[0017]

When mixing two kinds of fillers having different average particle diameters into a matrix resin liquid by a continuous ball mill, first, a smaller filler having an average particle diameter of 1 μm or less is sufficiently dispersed in the matrix resin liquid. Until mixed.
Next, a larger filler having an average particle size of 2 μm or more is added to the mixture and mixed again. After the smaller filler having an average particle size of 1 μm or less, which is difficult to disintegrate, is mixed until it is sufficiently dispersed in the matrix resin liquid, and then the larger filler is added and mixed again. The time for mixing is shortened, and breakage and cracks are less likely to occur.

According to the second aspect of the present invention, before the kneading by the continuous ball mill, the ultrasonic treatment is carried out with the smaller filler having an average particle size of 1 μm or less immersed in the solvent of the matrix resin liquid. Done. By this treatment, the solvent sufficiently permeates between the fillers in the aggregated state, and a part of the fillers in the aggregated state is broken. Next, the processing solution was mixed with a matrix resin solution having an average particle size of 2 μm.
The larger filler described above is added, and a mixing process is performed by a continuous ball mill. Since the solvent is sufficiently soaked in advance between the smaller fillers in the agglomerated state, even when the mixing process by the continuous ball mill is short, it is uniformly dispersed, and the time when the larger filler is mixed by the ball mill Is shortened, and breakage and cracks are less likely to occur.

According to the third aspect of the present invention, first, the filler having an average particle diameter of 1 μm or less and the solvent of the matrix resin liquid are mixed, and the aggregated filler is crushed. Since the solvent easily permeates between the fillers in the aggregate state than the matrix resin liquid, the fillers are crushed in a short time. Then, the matrix resin liquid and the larger filler having an average particle diameter of 2 μm or more are added to the mixture, and the mixture is again mixed, whereby the filler is uniformly dispersed in the matrix resin liquid.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below more specifically based on embodiments. (Example 1) 40 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001) and 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154) 5 parts by weight of an imidazole-type curing agent (manufactured by Shikoku Chemicals, trade name: 2PHZ) and 10 parts by weight of epoxy resin fine particles (manufactured by Toray, trade name: Trepal EP-B, average particle size: 0.5 μm) as a small filler. And 75 parts by weight of butyl cellosolve acetate were weighed and mixed using a homodisper stirrer.

Next, the mixture was mixed eight times using a continuous ball mill (pearl mill (manufactured by Ashizawa, trade name: ST1RL-V)) under the conditions of 0.2 l / min and 3000 rpm. The viscosity of the resulting mixture was 3000 cps. At this time, the epoxy resin fine particles having an average particle size of 0.5 μm were completely dispersed. Next, 25 parts by weight of an epoxy resin fine particle (trade name: Trepearl EP-B, average particle size: 5.5 μm) as a large filler was added to the mixture, and 0.2 l / min.
The mixture was mixed twice at each condition of 00 rpm to obtain an adhesive composition. In the adhesive composition thus obtained, not only the epoxy resin particles having an average particle size of 0.5 μm are completely dispersed, but also the epoxy resin particles having an average particle size of 5.5 μm are broken or cracked. Was not recognized.

The adhesive composition was applied on a substrate, dried and cured by heating to form an adhesive layer having a thickness of 20 μm. The adhesive layer was immersed in a solution of chromic acid aqueous solution to roughen the surface of the adhesive layer. Then, electroless copper plating was applied to the surface of the adhesive layer, and the adhesion strength of the electroless copper plating film was measured by the method of JIS-C-6481. As a result, the peel strength was 1.6 kg /
cm.

(Comparative Example) Each composition of Example 1 was weighed in the same manner as in Example 1, and was weighed in a pearl mill at 0.2 l / min.
The mixture was mixed eight times at each condition of 000 rpm to obtain an adhesive composition. Although the epoxy resin particles having an average particle size of 0.5 μm in the obtained adhesive composition were completely dispersed, all the epoxy resin particles having an average particle size of 5.5 μm were broken or cracked.

Using this adhesive composition, electroless copper plating is applied to the surface of the adhesive layer formed on the substrate under the same conditions as in the above embodiment, and the adhesion strength of the electroless copper plating film is measured according to JIS.
It measured by the method of -C-6481. As a result, the peel strength was only 1.0 kg / cm.

(Example 2) Fine particles of epoxy resin as a small filler (trade name: Trepal EP-, manufactured by Toray)
B, 10 parts by weight of an average particle size of 0.5 μm) and 75 parts by weight of butyl cellosolve acetate were weighed, and the filler was pulverized by applying ultrasonic waves, and then a bisphenol A type epoxy resin (trade name, manufactured by Yuka Shell Co., Ltd.) : E-1001) 40 parts by weight, 60 parts by weight of phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154), and 5 parts by weight of imidazole type hardener (manufactured by Shikoku Chemicals, trade name: 2PHZ) Was added and mixed using a homodisper stirrer.

Next, the mixture was added to a pearl mill (manufactured by Ashizawa, trade name: ST1RL-V) at 0.2 l / mi.
n, and mixed four times under each condition of 3000 rpm. The viscosity of the resulting mixture was 3000 cps. At this time, the epoxy resin fine particles having an average particle size of 0.5 μm were completely dispersed. Next, an epoxy resin fine particle (manufactured by Toray, trade name: Trepearl EP) as a large filler is added to the mixture.
-B, an average particle size of 5.5 μm) was added, and the mixture was mixed twice with a pearl mill under the conditions of 0.2 l / min and 1000 rpm to obtain an adhesive composition.

In this embodiment, the fine particles of the epoxy resin having a small average particle diameter, which are difficult to disintegrate, are subjected to ultrasonic treatment in advance in butyl cellosolve acetate, so that the solvent sufficiently permeates between the fine particles in the agglomerated state and partially disintegrates. Since the mixing was performed by a ball mill in a crushed state, the number of kneading was １ ／ of that in Example 1, and sufficient dispersion was obtained.

(Example 3) Epoxy resin fine particles as a small filler (trade name: Trepal EP-, manufactured by Toray Industries, Inc.)
B, 10 parts by weight of an average particle diameter of 0.5 μm), 5 parts by weight of an imidazole-type curing agent (trade name: 2PHZ, manufactured by Shikoku Chemicals), and 75 parts by weight of butyl cellosolve acetate are weighed, and are weighed using a homodisper stirrer. After mixing, it was left for one day.

After the filler is dispersed in the above mixture by applying ultrasonic waves, a pearl mill (manufactured by Ashizawa, trade name: ST) is used.
1 RL-V), 0.2 l / min, 3000 rpm
The mixture was mixed once under the condition of m.

To the above mixture, 10 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001) and 15 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154) Parts were added and mixed.

Next, 10 parts by weight of a bisphenol A type epoxy resin and 15 parts by weight of a phenol novolak type epoxy resin were added and mixed. This operation was repeated four times in total to mix.

In the same manner as in Example 1, epoxy resin fine particles (trade name: Trepal EP-B, manufactured by Toray, average particle size: 5.5 μm) as a large filler were added and mixed to obtain an adhesive composition. Was.

(Example 4) Epoxy resin fine particles as a small filler (trade name: Trepal EP-, manufactured by Toray)
B, 10 parts by weight of average particle size 0.5 μm) and 60 parts by weight of butyl cellosolve acetate were weighed and mixed using a homodisper stirrer. Next, the mixture was mixed eight times using a pearl mill (manufactured by Ashizawa, trade name: ST1RL-V) under the conditions of 0.2 l / min and 3000 rpm.

Next, epoxy resin fine particles (made by Toray, trade name: Trepal EP) as a large filler are added to the mixture.
-B, 25 parts by weight of an average particle diameter of 5.5 μm, and bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1)
001) 40 parts by weight, 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154), and an imidazole type curing agent (manufactured by Shikoku Chemicals, trade name: 2)
PHZ) 5 parts by weight and butyl cellosolve acetate 15
Parts by weight and 0.2 l / min in a pearl mill,
The mixture was mixed twice at each condition of 3000 rpm to obtain an adhesive composition.

In each of the above embodiments, by controlling the temperature at the time of mixing to be lower than the temperature at which the progress of the curing reaction of the resin and the volatilization of the solvent are suppressed, it is possible to prevent the viscosity of the mixture from increasing and the mixing efficiency from decreasing. can do. If the viscosity at the time of mixing is 1000 cps or less, the mixing efficiency is increased.

[0036]

As described above in detail, according to the present invention, a small filler composed of fine particles having an average particle diameter of 1 μm or less, which is difficult to disintegrate, and a large filler having an average particle diameter of 2 μm or more, which is easily broken, are used as a matrix. It can be uniformly mixed with the resin liquid without destruction of the filler, and the reliability of the additive method can be improved.

In addition, in addition to the above effects, the method according to the second and third aspects can shorten the mixing time by a ball mill required for uniformly dispersing the smaller filler in the matrix resin liquid. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an adhesive layer formed by the adhesive of the present invention before a roughening treatment.

FIG. 2 is a cross-sectional view schematically showing an adhesive layer after a roughening process.

FIG. 3A is a cross-sectional view schematically showing an adhesive layer formed by an adhesive before a roughening treatment when a mixing time by a continuous ball mill is long, and FIG. 3B is a cross-sectional view when a mixing time is short. FIG. 4 is a cross-sectional view schematically showing an adhesive layer before roughening formed by the adhesive of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Adhesive layer, 4a ... Smaller filler, 4
b: Larger filler, 5: Recess.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08J 3/20 B29B 7/00 C23C 18/18-18/26 H05K 3/18

Claims (3)

(57) [Claims] 1. A matrix resin solution which becomes hardly soluble in a solution by a curing treatment, and two kinds of fillers which are soluble in the solution and are hardly soluble in the matrix resin solution and have different average particle diameters. 4a, 4b) are kneaded in a continuous ball mill, the smaller filler (4a) having an average particle size of 1 μm or less is first mixed with a matrix resin liquid and dispersed, and then the mixture has an average particle size of A method for producing an adhesive for electroless plating, comprising adding a larger filler (4b) of 2 μm or more, mixing and dispersing again. 2. A matrix resin solution which becomes hardly soluble in a solution by a curing treatment, and two kinds of fillers which are soluble in the solution and hardly soluble in the matrix resin solution and have different average particle diameters. 4a) and 4b) are kneaded with a continuous ball mill, before the kneading with a continuous ball mill, the smaller filler (4a) having an average particle size of 1 μm or less.
Is immersed in the solvent of the matrix resin solution, and then subjected to ultrasonic treatment. Then, the matrix resin solution and the larger filler (4b) having an average particle diameter of 2 μm or more are added to the treatment solution and mixed by a ball mill. A method for producing an adhesive for electroless plating, comprising performing a treatment. 3. A matrix resin solution which becomes hardly soluble in a solution by a curing treatment, and two types of fillers which are soluble in the solution and hardly soluble in the matrix resin solution and have different average particle diameters. 4a, 4b) are kneaded with a continuous ball mill, first, the smaller filler (4a) having an average particle diameter of 1 μm or less and the solvent of the matrix resin liquid are mixed and dispersed, and then the mixture is added to the mixture. The matrix resin liquid and the larger filler having an average particle size of 2 μm or more (4
A method for producing an adhesive for electroless plating, wherein b) is added, mixed again and dispersed.